The present invention relates to one component alkoxy-functional room temperature vulcanizable (RTV) compositions. More particularly, the present invention relates to such one component alkoxy-functional RTV compositions having novel scavenger compositions or integrated scavenger/crosslinker compositions incorporated therein.
An early one component alkoxy-functional RTV composition is disclosed in Nitzsche et al., U.S. Pat. No. 3,065,194. Therein is is taught that a mixture of an end-blocked dimethylsiloxane polymer such as, for example, hydroxy or alkoxy end-blocked, an inert filler, ethylorthosilicate and dibutyltindilaurate can be vulcanized upon contact with water after a 14 day shelf period at room temperature. However, during preparation of the RTV composition the various ingredients of the mixture have to be vigorously dried by heating for one hour at 200.degree. C., and the RTV composition, after a relatively short shelf period, has to be drenched with water to effect curing.
Improved results toward combining the advantages of a noncorrosive acid-free polyalkoxysilane crosslinking agent with a silanol-terminated polydiorganosiloxane as a one package system are described in Weyenberg, U.S. Pat. No. 3,334,067, Cooper et al., U.S. Pat. No. 3,542,901, and Smith et al., U.S. Pat. Nos. 3,689,454 and 3,779,986. These disclosures utilize various titanium chelates as condensation catalysts in place of tin soap catalysts to accelerate cure of the RTV composition. One shortcoming of such one package systems was that after they were allowed to age for a period of five hours or more, the tack-free time of the aged RTV composition was considerably longer than the tack-free time of the same mixture after it was initially mixed and immediately exposed to atmospheric moisture.
Recently a shelf-stable, fast-curing, one component alkoxy-functional RTV composition was disclosed in the co-pending patent application of White et al., Ser. No. 277,524, filed June 26, 1981, now U.S. Pat. No. 4,395,526, and assigned to the same assignee as the present invention. Basically White et al. disclose that moisture curable polyalkoxy-terminated organopolysiloxane. RTV compositions can be made by combining (1) a silanol terminated polydiorganosiloxane; (2) a crosslinking silane; (3) an effective amount of certain silane scavengers for chemically combined hydroxy radicals; and (4) an effective amount of a condensation catalyst. The scavenger, which can be either a separate compound or part of the alkoxy-functional crosslinking agent, has a functionality selected from the group consisting of oximato, carbamato, enoxy, amino, amido, imidato, ureido, isocyanato and thioisocyanato.
Other scavenger compositions that may be utilized in the White et al. one component, alkoxy functional RTV composition are disclosed in copending patent applications by Dziark, Ser. No. 349,695, filed Feb. 17, 1982, now U.S. Pat. No. 4,417,042; Lucas, Ser. No. 449,105, filed Dec. 13, 1982; Chung et al., Ser. No. 428,038, filed Sept. 29, 1982; Chung et al., Ser. No. 437,895, filed Nov. 1, 1982, now abandoned, and Chung, Ser. No. 338,518, filed Jan. 11, 1982, now U.S. Pat. No. 4,424,157, all of which are assigned to the same assignee as the present invention and incorporated by reference into the instant disclosure.
Although each of the aforementioned patent applications discloses scavenger compositions and/or integrated scavenger/crosslinker compositions useful in RTV systems of the type disclosed by White et al., it was not heretofore appreciated that compounds other than silanes and silazanes can be effective scavenger or integrated scavenger/crosslinker compositions.
Accordingly, the present invention provides additional scavenger and integrated scavenger/crosslinker compositions which do not rely upon having silane or silazane functionality or structure. That is, scavengers provided by the present invention include compositions having chemical bonding between, for example, silicon and silicon, silicon and phosphorous, silicon and carbon, and silicon and oxygen.
It is therefore an object of the present invention to provide novel scavengers for one component alkoxy-functional RTV compositions which make such RTV compositions shelf-stable and fast-curing.
It is another object of the present invention to provide non-corrosive, one component alkoxy-functional RTV compositions that are shelf-stable and fast curing.
It is a further object of the present invention to provide a process for producing a relatively inexpensive, noncorrosive, one component RTV composition which is shelf-stable and fast-curing and which does not have an objectionable odor.
Other objects and advantages of the present invention will be obvious from the following detailed description.